Semiconductors are fabricated by subjecting a workpiece to a plurality of processes. Some of these processes including deposition, etching and ion implantation. To perform an ion implant, a dopant material may be used. This dopant material may be in the form of a gas, liquid or solid. To perform an etching process, an etching material may be used. Similarly, a suitable material may be used for deposition processes. Thus, in all of these processes, there may be a material of interest, which may be a gas, liquid or solid. The material of interest is often stored in a container, such as an ampoule.
While the process is being performed, it may be advantageous to monitor the amount of the material of interest. For example, if the material of interest is exhausted, the workpieces being processed will be flawed. Further, unexpected downtime is experienced to remove and replace the container holding the material of interest.
The amount of remaining material may be monitored for certain materials. For example, if the material of interest is a gas, the flow rate of the gas can be used to determine the amount of material remaining. A similar approach may be used if the material of interest is a liquid.
Unfortunately, measuring the amount of remaining material is more complex if the material of interest is a solid. Typically, the material of interest is extracted by allowing a carrier gas to flow into the container. The carrier gas draws the gaseous phase material of interest which is evaporated inside the container. Since carrier gas is flowing into the container, and a gaseous phase material is flowing from the container, an accurate measure of the flow rate of the material of interest is very difficult.
Therefore, an apparatus that allows the amount of material remaining within a container to be determined would be beneficial. It would be advantageous if the apparatus was able to monitor the amount of the material continuously.